Children's interaction with their environment, including written and spoken language and many perceptual-motor responses, is dependent in part on the ability to detect, remember, and utilize sequential information, predictability, and redundancy from a series of events. This research explores one critical aspect of this ability: children's apparently greater sensitivity to repeated events. School-age children, like adults, typically show a reaction-time advantage for repeated versus nonrepeated signals. In most cases the size of this repetition effect decreases as age increases. The proposed research is intended to further describe and explain developmental changes in the magnitude of the reaction-time repetition effect and to isolate factors which may contribute to these differences. Work to date has focused on age-related differences in the relative contributions of stimulus repetition and response and also address age-related differences in (1) the influence of the number of possible responses and the time between responses and (2) possible higher-order effects which can be attributed to events prior to the immediately preceding response.